3d printing of an intraocular lens having smooth, curved surfaces

ABSTRACT

A continuous additive fabrication system comprises a bath of photopolymer resin and a light source assembly having a light source and a motorized variable aperture. The light source assembly is operable to generate a focus point in the bath of photopolymer resin, the shape of the focus point at a curing plane within the bath of photopolymer resin corresponding to the shape of the motorized variable aperture. The continuous additive fabrication system further comprises a platform configured to support a build object and a drive mechanism (coupled to at least one of the platform and the light source assembly) configured to continuously move the curing plane through the bath of photopolymer resin. A size and/or shape of the motorized variable aperture is changed while the curing plane in continuously moved through the bath of photopolymer resin.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/920,495, filed Mar. 14, 2018, which claims priority to U.S.Provisional Application No. 62/474,658, filed Mar. 22, 2017. The entirecontents of each of these applications are incorporated by reference intheir entirety.

FIELD

This present disclosure relates generally 3D printing and, moreparticularly, to 3D printing of intraocular lenses having smooth, curvedsurfaces.

BACKGROUND

3D printing, also known as additive manufacturing, refers to processesused to create a three-dimensional object in which successive layers ofmaterial are formed under computer control to create an object. Thereare several 3D printing processes that differ in the way layers aredeposited to create parts and in the materials that are used.Stereolithography (SLA) is a type of 3D printing process that produceslayers of a solid part by curing liquid materials usingphotopolymerization. This is a process by which a vat of liquid polymeris exposed to light, causing chains of molecules to link together andform polymers that comprise one layer of a three-dimensional solidobject. A build plate on which the solid object rests, is then moveddown in small increments and the liquid polymer is again exposed tolight. The process repeats until a model of the object is complete.

Current SLA 3D printers use an image-forming projection system (e.g., adigital micromirror device (DMD), lithography, LCD, raster scan and thelike) to project an image on to a particular plane of a photopolymerbath. These systems are meant for creating complex shapes and so requirean adaptable image to cure the material. However, most image-formingprojection systems utilize pixels to project the image, and thus theprojected image has a resolution limitation in a transverse planerelated to the pixel size. Additionally, stepper motors for translatingthe build plane results in the curing of fixed incremental layer steps,resulting in a “stair-stepped” surface finish on the part, instead of apart having smooth surfaces. Due to these limitations, current SLA 3Dprinters may not be suitable for production of intraocular lenses (IOLs)as the “stair steps” can reduce optical quality and cosmetic appearance.

Accordingly, what is needed is an improved 3D printing system suitablefor producing miniature optics, including IOLs, having smooth,continuously curved surfaces.

SUMMARY

In certain embodiments, a continuous additive fabrication systemcomprises a bath of photopolymer resin and a light source assemblyhaving a light source and a motorized variable aperture. The lightsource assembly is operable to generate a focus point in the bath ofphotopolymer resin, the shape of the focus point at a curing planewithin the bath of photopolymer resin corresponding to the shape of themotorized variable aperture. The continuous additive fabrication systemfurther comprises a platform configured to support a build object and adrive mechanism (coupled to at least one of the platform and the lightsource assembly) configured to continuously move the curing planethrough the bath of photopolymer resin. A size and/or shape of themotorized variable aperture is changed while the curing plane incontinuously moved through the bath of photopolymer resin.

In certain embodiments, a method for continuous additive fabricationcomprising generating, via a light source assembly, a focus point in abath of photopolymer resin, the shape of the focus point at a curingplane within the bath of photopolymer resin corresponding to the shapeof a motorized variable aperture of the light source assembly. Themethod further comprises changing a size and/or shape of the motorizedvariable aperture while continuously moving the curing plane through thebath of photopolymer resin.

The above-described systems and methods may provide certain advantagesover conventional additive manufacturing techniques. For example, theabove-described systems and methods may allow for the generation ofsmooth, high-resolution, optical-quality surfaces, suitable for IOLs.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and theadvantages thereof, reference is now made to the following descriptiontaken in conjunction with the accompanying drawings in which likereference numerals indicate like features and wherein:

FIG. 1 is a diagram illustrating a portion of an example conventionalSLA additive fabrication system;

FIG. 2 is a diagram illustrating a continuous additive fabricationsystem in accordance with exemplary embodiments of the presentdisclosure; and

FIG. 3 is a cross-section diagram of light source assembly showing thelight source and the motorized variable aperture.

DETAILED DESCRIPTION

Exemplary embodiments of the present disclosure relate to a continuousadditive fabrication system. The following description is presented toenable one of ordinary skill in the art to make and use the inventionand is provided in the context of a patent application and itsrequirements. Various modifications to the exemplary embodiments and thegeneric principles and features described herein will be readilyapparent. The exemplary embodiments are mainly described in terms ofparticular methods and systems provided in particular implementations.However, the methods and systems will operate effectively in otherimplementations. Phrases such as “exemplary embodiment”, “oneembodiment” and “another embodiment” may refer to the same or differentembodiments. The embodiments will be described with respect to systemsand/or devices having certain components. However, the systems and/ordevices may include more or less components than those shown, andvariations in the arrangement and type of the components may be madewithout departing from the scope of the invention. The exemplaryembodiments will also be described in the context of particular methodshaving certain steps. However, the method and system operate effectivelyfor other methods having different and/or additional steps and steps indifferent orders that are not inconsistent with the exemplaryembodiments. Thus, the present invention is not intended to be limitedto the embodiments shown, but is to be accorded the widest scopeconsistent with the principles and features described herein.

FIG. 1 is a diagram illustrating a portion of an example conventionalSLA additive fabrication system. The example SLA additive fabricationsystem 10, e.g., a conventional SLA 3D printer, includes a digitalmicromirror device (DMD) 12 or other image-forming projection system, toproject images 14 on to a transverse plane 16 of a bath of photopolymerresin 18. Typically, the images 14 are projected by the DMD 12 byfocusing an ultraviolet (UV) light/laser (not shown) on to thetransverse plane 16 of photopolymer resin 18. A DMD chip comprisesseveral hundred thousand microscopic mirrors on its surface arranged inan array corresponding to the pixels in the image 14 to be displayed.The ultraviolet light projected by the DMD causes the photosensitivephotopolymer to solidify to form a layer of the cured polymer definingthe resulting part. However, because the DMD 12 is made up of pixels,the projected images 14 have a resolution limitation in the transverseplane 16 related to the pixel size of the DMD 12, resulting in“stair-stepped” edges of the images 14, as shown.

Additionally, stepper motors (not shown) translate an elevator apparatusor platform up or down in the bath photopolymer resin 18 a distanceequal to the thickness of a single layer of the resulting part 20 andthe photopolymer is again exposed by the UV light. This process isrepeated for each layer of the design until the 3D object is complete.

The use of stepper motors for translating the assembly results in curingfixed incremental layer steps, also resulting in a “stair-stepped”surface finish for each layer of the resulting part 20 in a direction ofthe motor movement, shown here as the motor movement plane 22. Thus,conventional SLA additive fabrication systems create resulting parts 20having what could be considered aliasing in both the transverse (orhorizontal) direction and the motor (or vertical) direction, instead ofparts having smooth surfaces. For an object, such as an intraocular lens(IOL), which is implanted into a human eye, having such aliased surfaceswould be unacceptable due to reduced optical quality and cosmeticappearance.

The exemplary embodiments provide an improved continuous additivefabrication method and system that continually moves a curing plane upthrough a volume of photopolymer resin utilizing a combination of acontinuously-driven servo motor for linear positioning with a motorizedvariable aperture in the light source to create smooth, continuouslycurved surfaces, which are suitable for intraocular lens (IOL)construction.

FIG. 2 is a diagram illustrating a continuous additive fabricationsystem in accordance with exemplary embodiments of the presentdisclosure. The continuous additive fabrication system 100 may beimplemented as a 3D printer that includes a bath of a photopolymer resin102, a light source assembly 104, a platform 106 located within the bathof a photopolymer resin 102 that supports cured polymer 108 (the objectbeing built/printed), a drive mechanism 110 coupled to the light sourceassembly 104 and/or the platform 106, and a processor 111 coupled to thelight source assembly 104 and to the drive mechanism 110.

Photopolymer resin 102 may refer to any type of suitable polymerizableliquids, monomers, initiators and combinations thereof. The continuousadditive fabrication system 100 may also include a photopolymer resinreservoir (not shown) for replenishing the path of photopolymer resin102 during the building process.

Drive mechanism 110 may refer to any suitable device for moving lightsource assembly 104 and/or the platform 106. For example, drivemechanism 110 may comprise one or more a servo motors, electric motors,linear actuators, or any other suitable motor or actuation device.

According to the exemplary embodiments, the light source assembly 104 isprovided with a light source 112 and a motorized variable aperture 114.The light source 112 may comprise an ultraviolet (UV) light source andmay include conventional optical components (not shown) such as, forexample, one or more LEDs, filters, condensers, diffusers, lens tubelength adjusters, and the like. Although in the exemplary embodimentdiscussed above the light source 112 comprises a UV light source, lightsource 112 may alternatively comprise any suitable type of excitationsource (e.g., a light source generating light in the visible or otherspectra). Additionally, although in the exemplary embodiment discussedabove the light source 112 includes one or more LEDs for generatinglight, light source 112 may alternatively include any other suitablecomponents for generating light (e.g., incandescent lights, fluorescentlights, phosphorescent or luminescent light, or lasers).

FIG. 3 is a cross-section diagram of the light source assembly 104showing the light source 112 and the motorized variable aperture 114.Also shown is an enlarged area of the drawing (dashed oval) of theemitted light and the photopolymer resin 102. The light source assembly104 may be mounted vertically above the photopolymer resin 102 and thelight 120 emitted from the light source assembly 104 may have a focuspoint that defines a curing plane 124 within the photopolymer resin 102.In one embodiment, the focus point may comprise a circular image of theaperture. As discussed in further detail below, adjustment of thevariable aperture and continuous movement of the platform 106 relativeto the curing plane 124 (or, alternatively, movement of the light sourceassembly 104 relative to the platform 106) may allow for the generationof parts (e.g., IOLs) having smooth curved surfaces.

Referring now to both FIGS. 2 and 3, during the building process, aprocessor 111 may execute software instructions, referred to herein as acuring control module 116, and those software instructions may configurethe processor 111 to control both the drive mechanism 110 and the lightsource assembly 104. The processor 111 may control, among other things,a diameter of the motorized variable aperture 114, the intensity of thelight 120, and the drive mechanism 110 to adjust a position of theplatform 106 and/or the position of the light source assembly 104.

In one embodiment, the processor 111 may initially position the platform106 at a predetermined depth below the surface 122 of the photopolymerresin 102 and set the focus point of the light 120, and therefore, aninitial position of the curing plane 124, a predetermined distance abovethe platform 106. The predetermined depth at which the platform 106 isinitially positioned may be based at least in part on the height of thebuild object. In one embodiment, a UV-blocker may be used to control thedepth of penetration of light 120 into the photopolymer resin 102.

During the building process, the processor 111 may cause the lightsource assembly 104 to constantly expose the photopolymer resin 102 withprojections of the motorized variable aperture onto the curing plane 124in the photopolymer resin 102. In one embodiment, if the motorizedvariable aperture is circular in shape, then the projections will becircular as well. Additionally or alternatively, the projection may bemodified to produce other shapes as well, such an elliptical shape toproduce an asymmetric optic. In certain embodiment, the projections ofthe motorized variable aperture 114 may be reimaged with a magnificationfactor onto the curing plane 124.

During the exposure, the processor 111 may cause a change in thediameter of the motorized variable aperture 114 according to a shape ofthe build object, while continuously moving the curing plane 124 throughthe bath of photopolymer resin 102. Stated differently, the processor111 may control a continuous photo-curing process in which continuousmovement of the curing plane 124 is synchronized with changes to thediameter of the motorized variable aperture and changes to position ofthe light 120 emitted from the light source assembly 104 to create abuild object having smooth surfaces in both transverse and verticaldirections.

In one embodiment, the curing plane 124 may be continuously moved upthrough the photopolymer resin by continuously moving the light sourceassembly 104 vertically up and away from the surface 122 of thephotopolymer resin 102, thereby moving the curing plane 124 verticallythrough the photopolymer resin 102 towards the surface 122 of thephotopolymer resin 102. In this embodiment, aperture changes may besynchronized with the speed of the drive mechanism 110 and optionallywith properties of the light source, while the position of the platform106 may remain fixed.

In another embodiment, the curing plane 124 may be continuously moved upthrough the photopolymer resin by continuously changing an optical powerof the light source assembly 104 to thereby move the curing plane 124vertically through the photopolymer resin 102 towards the surface 122 ofthe photopolymer resin 102. In this embodiment, the optical power of thelight source assembly 104 may be reduced, while the position of theplatform 106 may remain fixed.

According to yet another embodiment, the curing control module 116 mayconfigure the processor 111 to change the diameter of the motorizedvariable aperture 114 according to a shape of the build object, whilecontinuously moving the platform 106 vertically away from the surface122 of the photopolymer resin 102, thereby continuously lowering thebuild object during the curing process. In this embodiment, aperturechanges are synchronized with the speed of the drive mechanism 110 andoptionally with properties of the light source, while the position ofthe curing plane remains fixed.

In one embodiment, the speed at which the curing plane 124 is movedvertically may be fixed or variable, and the speed at which the diameterof the motorized variable aperture 114 is changed is dependent upon thespeed of the vertical movement as well as the shape of the build object.Additionally, calculated parameters may be used during the curingprocess to vary proportional speed of the drive mechanism 110 usingcalculated curing control parameters to create surfaces (e.g., for IOLs)with spherical, aspherical, or free-form optical surfacecharacteristics. In one embodiment, the curing control parameters inputto the curing control module 116 may include an output shape geometryfor the build object, an aperture control profile for the motorizedvariable aperture 114, a motion control profile for the drive mechanism110, and light source assembly profile for the light source 112. Forinstance, when creating a hemisphere shape, for example, the speed atwhich the diameter of the motorized variable aperture 114 is changingwould not be constant for a particular speed of the drive mechanism 110.If the drive mechanism 110 is moving at a constant speed to move thelight source assembly 104 and/or the platform 106, the control module116 may alter the diameter of the motorized variable aperture 114according to an equation defining the output shape geometry.

The above-described processor 111 may be incorporated into the 3Dprinter or in a computer coupled to the 3D printer. In both embodiments,a memory (not shown) may be coupled to the processor 111. The memory maybe used to store software instructions comprising the curing controlmodule 116, as well as the curing control parameters. The processor 111may be configured to execute the instructions stored in a memory tocause and control the process as described in this disclosure. As usedherein, a processor may comprise one or more microprocessors,field-programmable gate arrays (FPGAs), controllers, or any othersuitable computing devices or resources, and memory may take the form ofvolatile or non-volatile memory including, without limitation, magneticmedia, optical media, random access memory (RAM), read-only memory(ROM), removable media, or any other suitable memory component. Memorymay store instructions for programs and algorithms that, when executedby the processor, implement the functionality described herein withrespect to any such processor, memory, or component that includesprocessing functionality.

A method and system for a continuous additive fabrication system hasbeen disclosed. The present invention has been described in accordancewith the embodiments shown, and there could be variations to theembodiments, and any variations would be within the spirit and scope ofthe present invention. For example, the exemplary embodiment can beimplemented using hardware, software, a computer readable mediumcontaining program instructions, or a combination thereof. Accordingly,many modifications may be made by one of ordinary skill in the artwithout departing from the spirit and scope of the appended claims.

We claim:
 1. A continuous additive fabrication system for forming anintraocular lens (IOL), comprising: a bath of photopolymer resin; alight source assembly comprising a light source and a motorized variableaperture, the light source assembly configured to generate a focus pointin the bath of photopolymer resin, a shape of the focus point at acuring plane within the bath of photopolymer resin corresponding to ashape of the motorized variable aperture; and a drive mechanism coupledto the light source assembly, the drive mechanism configured to move thecuring plane through the bath of photopolymer resin by moving the lightsource assembly vertically up and away from a surface of thephotopolymer resin, thereby moving the curing plane vertically throughthe photopolymer resin towards the surface of the photopolymer resin,wherein the drive mechanism is further configured to vary a speed thatthe light source assembly moves away from the surface of thephotopolymer resin according to calculated parameters to create anaspherical surface on the IOL, wherein the motorized variable apertureis configured to change a diameter thereof at a rate that varies as thelight source assembly is moved away from the surface of the photopolymerresin so as to form the IOL with a smooth hemispherical shape.
 2. Thecontinuous additive fabrication system of claim 1, further comprising aplatform within the bath of photopolymer resin configured to supportcured polymer comprising a build object.
 3. The continuous additivefabrication system of claim 2, wherein a position of the platformlocated within the bath of photopolymer resin remains fixed.
 4. Thecontinuous additive fabrication system of claim 1, wherein an initialposition of the curing plane is set at a predetermined distance above aplatform located within the bath of photopolymer resin.
 5. A continuousadditive fabrication system, comprising: a bath of photopolymer resin; alight source assembly comprising a light source and a motorized variableaperture, the light source assembly operable to generate a focus pointin the bath of photopolymer resin, a shape of the focus point at acuring plane within the bath of photopolymer resin corresponding to ashape of the motorized variable aperture; a platform configured tosupport cured polymer comprising a build object; a drive mechanismcoupled to at least one of the platform or the light source assembly,the drive mechanism configured to continuously move at least one of thecuring plane or the platform through the bath of photopolymer resin,wherein at least one of a size or shape of the motorized variableaperture is changed while the at least one of the curing plane or theplatform is continuously moved through the bath of photopolymer resin.6. The continuous additive fabrication system of claim 5, wherein thecuring plane is continuously moved through the bath of photopolymerresin by continuously changing an optical power of the light sourceassembly to thereby move the curing plane vertically through thephotopolymer resin towards a surface of the photopolymer resin.
 7. Thecontinuous additive fabrication system of claim 6, wherein a position ofthe platform remains fixed.
 8. The continuous additive fabricationsystem of claim 6, wherein a rate of the change to the at least one ofthe size or shape of the motorized variable aperture is synchronizedwith a speed at which the curing plane is continuously moved verticallythrough the photopolymer resin.
 9. The continuous additive fabricationsystem of claim 5, wherein an initial position of the platform is set ata predetermined depth below a surface of the photopolymer resin and aninitial position of the curing plane is set at a predetermined distanceabove the platform.
 10. The continuous additive fabrication system ofclaim 5, wherein the drive mechanism is configured to continuously movethe platform vertically through the bath of photopolymer resin and awayfrom a surface of the photopolymer resin while the curing plane remainsfixed.
 11. The continuous additive fabrication system of claim 5,wherein the drive mechanism comprises a servo motor.
 12. A method forforming an intraocular lens (IOL) using continuous additive fabrication,comprising: generating, via a light source assembly, a focus point in abath of photopolymer resin, a shape of the focus point at a curing planewithin the bath of photopolymer resin corresponding to a shape of amotorized variable aperture of the light source assembly, wherein thebath of photopolymer resin comprises a platform disposed therein;continuously moving at least one of the curing plane or the platformthrough the bath of photopolymer resin by continuously changing anoptical power of the light source assembly to thereby move the curingplane vertically through the photopolymer resin towards a surface of thephotopolymer resin; and changing at least one of a size or shape of themotorized variable aperture while continuously moving the at least oneof the curing plane or the platform through the bath of photopolymerresin so as to form the IOL with a smooth hemispherical shape.
 13. Themethod of claim 12, wherein the curing plane is continuously moved bycontinuously changing an optical power of the light source assembly tothereby move the curing plane vertically through the photopolymer resintowards a surface of the photopolymer resin.
 14. The method of claim 13,wherein a position of the platform remains fixed.
 15. The method ofclaim 13, wherein a rate of the change to the at least one of the sizeor shape of the motorized variable aperture is synchronized with a speedat which the curing plane is continuously moved vertically through thephotopolymer resin.
 16. The method of claim 12, wherein the platform iscontinuously moved vertically through the bath of photopolymer resin andaway from a surface of the photopolymer resin while the curing planeremains fixed.
 17. The method of claim 12, wherein the IOL is supportedby the platform.